71 lines
2.2 KiB
Python
71 lines
2.2 KiB
Python
# cvr.py - functions for handling Danish CVR numbers
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#
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# Copyright (C) 2012, 2013 Arthur de Jong
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301 USA
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"""CVR (Momsregistreringsnummer, Danish VAT number).
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The CVR (Momsregistreringsnummer, VAT) is an 8 digit number with a
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straightforward check mechanism.
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>>> validate('DK 13585628')
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'13585628'
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>>> validate('DK 13585627')
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Traceback (most recent call last):
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...
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InvalidChecksum: ...
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"""
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from stdnum.exceptions import *
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from stdnum.util import clean
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def compact(number):
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"""Convert the number to the minimal representation. This strips the
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number of any valid separators and removes surrounding whitespace."""
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number = clean(number, ' -.,/:').upper().strip()
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if number.startswith('DK'):
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number = number[2:]
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return number
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def checksum(number):
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"""Calculate the checksum."""
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weights = (2, 7, 6, 5, 4, 3, 2, 1)
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return sum(weights[i] * int(n) for i, n in enumerate(number)) % 11
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def validate(number):
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"""Checks to see if the number provided is a valid VAT number. This checks
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the length, formatting and check digit."""
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number = compact(number)
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if not number.isdigit() or number[0] == '0':
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raise InvalidFormat()
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if len(number) != 8:
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raise InvalidLength()
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if checksum(number) != 0:
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raise InvalidChecksum()
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return number
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def is_valid(number):
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"""Checks to see if the number provided is a valid VAT number. This checks
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the length, formatting and check digit."""
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try:
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return bool(validate(number))
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except ValidationError:
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return False
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